1. Technical Field
The present invention relates to an electromagnetic switch including excitation coils that generate magnetomotive force when current is passed therethrough, and current-supply terminal members that supply current to the excitation coils upon reception of electric power from an external power supply.
2. Related Art
Electromagnetic switches are well known in which a plunger is driven by the attractive force of an electromagnet so that electrical contacts are opened/closed in synchronization with the movement of the plunger.
Such an electromagnetic switch uses a process in which current is passed, via current-supply terminal members, through excitation coils incorporated in a switch frame to allow the excitation coils to generate magnetomotive force by which the plunger is driven. Metal terminal plates, which are generally called blade-shaped terminals, are most frequently used as the current-supply terminal members for supplying current to the excitation coils. As disclosed in JP-A-2009-191843, for example, blade-shaped terminals each have one end which is directly or indirectly connected to an excitation coil in the electromagnetic switch, and the other end which is drawn out in the axial direction of the electromagnetic switch from inside and through a resin cover that covers an opening of the switch frame.
According to the terminal structure mentioned above, wiring work for the electromagnetic switch is facilitated. Specifically, in the wiring work, electric supply lines from outside are connected to the respective blade-shaped terminals. The connection is established by only directly fitting a power supply connector provided at the ends of the electric supply lines to the ends of the blade-shaped terminals (the ends of the blade-shaped terminals, which are drawn out of the resin cover).
Also, recently, a waterproof terminal structure is under development for the purpose of enhancing reliability of electromagnetic switches. FIG. 7 is a general side elevational view illustrating a starter installing an electromagnetic switch of conventional art. The electromagnetic switch shown in FIG. 7 has the terminal structure mentioned above and includes a resin cover 9, a power supply connector 23, and a connector fitting member 20a to be fitted to the power supply connector 23. In order to enhance waterproofing properties, the connector fitting member 20a is provided around the blade-shaped terminals, being integrated into the resin cover 9, while a piece of waterproof rubber, for example, is sandwiched between the connector fitting member 20a and the power supply connector 23. Owing to this terminal structure, an electromagnetic switch having good reliability is produced at low cost.
An electromagnetic switch may be installed in a vehicle starter and arranged in an engine compartment. In an increasing number of cases, however, the installation space in an engine compartment is restricted. This is because on-vehicle devices, such as engine accessories, are increasingly used recently and thus the interior of the engine compartment is crowded with these devices. In particular, in many cases, spatial constraints are imposed on an electromagnetic switch in its axial direction, when the engine in use is a transverse engine, or a small-displacement engine having a small number of cylinders.
Further, an electromagnetic switch to be installed in a vehicle starter may have the terminal structure as mentioned above, i.e. may use blade-shaped terminals that are metal terminal plates with the ends drawn out from inside and through a resin cover in the axial direction of the electromagnetic switch. When such an electromagnetic switch is used, the length of the axial projection in the terminal structure will add constraints to the installation of the switch, the axial projection including a power supply connector to be fitted to the ends of the blade-shaped terminals.